1. Field of the Invention
This invention relates to die forming by forming a material using a die, and more specifically to a composite die constituted of a plurality of die members formed of materials exhibiting different degrees of elastic deformation and to a method of die forming using the die in which a workpiece is formed to a desired shape by utilizing the different degrees of elastic deformation of the materials constituting the die members for controlling the elastic deformation of the die at the time of the forming operation.
2. Description of the Prior Art
In the field of die forming it is nowadays frequently necessary to subject a workpiece to a minute amount of forming on the micron order. This is true, for example, in the production of optical products, which often have to be imparted with minute changes in shape with high precision and good reproducibility.
In carrying out such forming by conventional die forming, the die is constituted and supported so as to resist elastic deformation. In producing a flat surface having minute irregularities (hills and valleys), therefore, it has been necessary to form the surface of the die to have a shape corresponding to the minute irregularities to be formed. With such a method, however, fabrication of the mold becomes increasingly difficult as the size of the irregularities becomes smaller.
In their earlier U.S. patent application Ser. No. 611,045, the inventors proposed a die forming method which overcomes this problem by using an elastically deformable die whose elastic deformation is controlled by the thickness distribution of the material constituting the die. While this earlier proposed method greatly simplifies the formation of minute irregularities, the fact that it utilizes the elastic deformation of a die having irregularities formed on its rear surface makes it necessary to use a thin die so that the application of the method to the processing of relatively hard materials such as metals is not possible unless special measures are adopted.
The object of this invention is to provide a die and a method of die forming using the die which, with a simple structural arrangement and without need for precision machining of the die surface, make it possible to impart minute changes in shape with high reproducibility to materials of both ordinary and high hardness.